The objective of the present studies is to examine the mechanisms of action of sex hormones on neural activity and hence on motor behavior. Studies by others have shown that when labelled dihydrotestosterone is administered to Xenopus laevis, the label is taken into the nucleus of the brachial motoneurons that distribute to the flexor muscles of the forelegs. Recordings from these motoneurons in castrated frogs or from male frogs induced by administration of anterior pituitary to "clasp" females, show differences in activity. Motoneurons from induced frogs respond to dorsal root stimulation with short latency monosynaptic responses and also display long-lasting repetitive activity. Similar effects can be brought about by adding dihydrotestosterone to the chamber while recording from the brachial motoneurons of the spinal cord from a castrated male frog. In the next year, the motoneurons from which the activity is recorded will be identified by intracellular injection of horseradish peroxidase; secondly, the specificity of action of dihydrotestosterone will be tested by using other steroids to see if they can influence the activity of these neurons; thirdly, antiandrogens that prevent the binding of the sex-hormone with the protein will be given to the bath to see if activity resulting from dihydrotestosterone can be prevented; and finally, protein synthesis inhibitors will also be added. In this way, it is hoped that the influence of these hormones on neural behavior will be clarified.